Skin-to-skin contact detection

ABSTRACT

Contact or movement gestures between a first body part and a second body part can be detected. Sense circuitry can be configured to sense a signal at the sense electrode (e.g., configured to contact the second body part) in response to a drive signal applied to the drive electrode (e.g., configured to contact the first body part). Processing circuitry can be configured to detect contact in accordance with a determination that one or more criteria are met (e.g., an amplitude criterion and a non-distortion criterion). Additionally or alternatively, processing circuitry can be configured to detect a movement gesture in accordance with a determination that one or more criteria are met (e.g., a contact criterion and a movement criterion).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part (CIP) of U.S. patentapplication Ser. No. 16/836,552, filed on Mar. 31, 2020, the contents ofwhich are incorporated by reference herein in their entirety for allpurposes.

FIELD

This relates generally to systems and methods of detecting skin-to-skincontact, and more particularly, to detecting contact between two handsor between two fingers for input in virtual reality or augmented realityenvironments.

BACKGROUND

Many types of input devices are presently available for performingoperations in a computing system, such as buttons or keys, mice,trackballs, joysticks, touch sensor panels, touch screens and the like.In some examples, contact between two different parts of a user's bodymay be used for input. For example, cameras in a head-mounted displaycan be used to track movement of fingers to detect a finger in contactwith an opposite hand, or to track movement of a finger along anopposite hand surface. Additionally or alternatively, aradiofrequency-based system can be used to detect a finger in contactwith an opposite hand, or to track movement of a finger along anopposite hand surface. However, camera-based systems and/orradiofrequency-based systems may have difficulty detecting thedifference between a finger touching the opposite hand or proximate towithout contacting (hovering above) the opposite hand. Additionally,camera-based systems require the finger and opposite hand be in thefield of view of the cameras for operation.

SUMMARY

This relates to devices and methods of detecting contact between a firstbody part and a second body part. Sense circuitry can be configured tosense a signal at the sense electrode (e.g., configured to contact thesecond body part) in response to a drive signal applied to the driveelectrode (e.g., configured to contact the first body part). Processingcircuitry can be configured to detect contact in accordance with adetermination that one or more criteria are met. The one or morecriteria can include a first criterion that is met when an amplitude ofthe sensed signal exceeds an amplitude threshold and a second criterionthat is met when the sensed signal has a non-distorted waveform. Using arobust set of criteria, including an evaluation of the quality of thewaveform (e.g., whether it is distorted or not), can improve thedisambiguation between a skin-to-skin contact event and a proximityevent.

This also relates to devices and methods of detecting a movement gestureusing contact between two fingers of the same hand (e.g., to enableone-handed skin-to-skin input gestures). Sense circuitry can beconfigured to sense a signal at a sense electrode (e.g., configured tocontact a finger of a hand) in response to a drive signal applied to adrive electrode (e.g., configured to contact a different finger of thehand). Processing circuitry can be configured to detect a movementgesture (e.g., a slide gesture) in accordance with a determination thatone or more criteria are met. The one or more criteria can include afirst criterion indicative of contact between a first finger and asecond finger and a second criterion indicative of movement of the firstfinger along the second finger.

This further relates to devices and methods of detecting gesturesbetween a finger of one hand and other body parts (e.g., other fingersor a thumb on the same hand, or the opposing hand) using a single device(e.g., a ring) on the finger of the hand. Sense circuitry in the devicecan be configured to sense a signal at one or more sense electrodes inthe device in response to a drive signal applied to a drive electrode inthe device. Processing circuitry can be configured to detect contact ora movement gesture (e.g., a slide gesture) in accordance with adetermination that one or more criteria are met. The one or morecriteria can include various amplitude criteria, in some instancesevaluated over a certain time period. When a particular gesture isdetected, an operation can be initiated.

This also relates to devices and methods of detecting gestures between afinger of one hand and other body parts (e.g., other fingers or a thumbon the same hand, or the opposing hand) using a device (e.g., a ring) oneach of multiple fingers of the same hand, or on fingers of differenthands. Sense circuitry in each device can be configured to sense asignal at one or more sense electrodes in the device in response todrive signals applied to a drive electrode in each of the devices. Whena particular gesture is detected, an operation can be initiated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1B illustrate an example system for skin-to-skin contactdetection according to examples of the disclosure.

FIG. 2 illustrates a block diagram of an example computing system 200for skin-to-skin contact detection according to examples of thedisclosure.

FIGS. 3A-3B illustrate a proximity and a contact, respectively, betweena first body part and a second body part according to examples of thedisclosure.

FIGS. 4A-4B illustrate time-domain and frequency domain representationsof the sensed signal corresponding to the proximity or the contactaccording to examples of the disclosure.

FIG. 5 illustrates a block diagram of a correlation circuit 500according to examples of the disclosure.

FIG. 6 illustrates an example process of skin-to-skin contact detectionaccording to examples of the disclosure.

FIGS. 7A-7B illustrate an example system for detection of a skin-to-skingesture according to examples of the disclosure.

FIGS. 8A-8C illustrate time-domain representations and frequency domainrepresentations of the sensed signal corresponding to a finger-to-fingerslide gesture according to examples of the disclosure.

FIG. 9 illustrates an example process of skin-to-skin gesture detectionaccording to examples of the disclosure.

FIG. 10 illustrates a wearable device in the form of a ring according toexamples of the disclosure.

FIG. 11 is a system block diagram of a wearable device according toexamples of the disclosure.

FIG. 12A illustrates a hand with an index finger supporting a wearabledevice (e.g., a ring) but not making contact with a thumb according toexamples of the disclosure.

FIG. 12B illustrates the hand of FIG. 12A, except that the index fingeris now making contact with the thumb according to examples of thedisclosure.

FIG. 12C illustrates a sense output signal when the index finger andthumb make and break contact as shown in FIGS. 12B and 12A according toexamples of the disclosure.

FIG. 13A illustrates a hand with an index finger supporting a wearabledevice (e.g., a ring) but not making contact with a middle fingeraccording to examples of the disclosure.

FIG. 13B illustrates the hand of FIG. 13A, except that the index fingeris now making contact with the middle finger according to examples ofthe disclosure.

FIG. 13C illustrates a sense output signal when the index finger andmiddle finger make and break contact as shown in FIGS. 13B and 13Aaccording to examples of the disclosure.

FIG. 14A illustrates a hand with an index finger supporting a wearabledevice (e.g., a ring) and in contact with a middle finger according toexamples of the disclosure.

FIG. 14B illustrates the hand of FIG. 14A, except that the thumb is nowmaking contact with the already touching index finger and middle fingeraccording to examples of the disclosure.

FIG. 14C illustrates a sense output signal when the thumb makes andbreaks contact with the already touching index finger and middle fingeras shown in FIGS. 14B and 14A according to examples of the disclosure.

FIG. 15A illustrates a hand with an index finger supporting a wearabledevice (e.g., a ring) and making contact with a thumb according toexamples of the disclosure.

FIG. 15B illustrates the hand of FIG. 15A, except that the middle fingeris now making contact with the already touching index finger and thumbaccording to examples of the disclosure.

FIG. 15C illustrates a sense output signal when the middle finger makesand breaks contact with the already touching index finger and thumb asshown in FIGS. 15B and 15A according to examples of the disclosure.

FIG. 16A illustrates a hand with an index finger supporting a wearabledevice (e.g., a ring) and making contact with an opposite hand accordingto examples of the disclosure.

FIG. 16B illustrates a left hand with an index finger supporting awearable device (e.g., a ring) and also a right hand with an indexfinger supporting another wearable device (e.g., a ring) according toexamples of the disclosure.

FIG. 16C illustrates a hand with an index finger supporting a wearabledevice (e.g., a ring) and a middle finger supporting another wearabledevice (e.g., a ring) according to examples of the disclosure.

FIG. 17 illustrates a flowchart for detecting input gestures using oneor more devices according to examples of the disclosure.

DETAILED DESCRIPTION

In the following description of examples, reference is made to theaccompanying drawings which form a part hereof, and in which it is shownby way of illustration specific examples that can be practiced. It is tobe understood that other examples can be used and structural changes canbe made without departing from the scope of the disclosed examples.

This relates to devices and methods of detecting contact between a firstbody part and a second body part. Sense circuitry can be configured tosense a signal at the sense electrode (e.g., configured to contact thesecond body part) in response to a drive signal applied to the driveelectrode (e.g., configured to contact the first body part). Processingcircuitry can be configured to detect contact in accordance with adetermination that one or more criteria are met. The one or morecriteria can include a first criterion that is met when an amplitude ofthe sensed signal exceeds an amplitude threshold and a second criterionthat is met when the sensed signal has a non-distorted waveform. Using arobust set of criteria, including an evaluation of the quality of thewaveform (e.g., whether it is distorted or not), can improve thedisambiguation between a skin-to-skin contact event and a proximityevent.

This also relates to devices and methods of detecting a movement gestureusing contact between two fingers of the same hand (e.g., to enableone-handed skin-to-skin input gestures). Sense circuitry can beconfigured to sense a signal at a sense electrode (e.g., configured tocontact a finger of a hand) in response to a drive signal applied to adrive electrode (e.g., configured to contact a different finger of thehand). Processing circuitry can be configured to detect a movementgesture (e.g., a slide gesture) in accordance with a determination thatone or more criteria are met. The one or more criteria can include afirst criterion indicative of contact between a first finger and asecond finger and a second criterion indicative of movement of the firstfinger along the second finger.

This further relates to devices and methods of detecting gesturesbetween a finger of one hand and other body parts (e.g., other fingersor a thumb on the same hand, or the opposing hand) using a single device(e.g., a ring) on the finger of the hand. Sense circuitry in the devicecan be configured to sense a signal at one or more sense electrodes inthe device in response to a drive signal applied to a drive electrode inthe device. Processing circuitry can be configured to detect contact ora movement gesture (e.g., a slide gesture) in accordance with adetermination that one or more criteria are met. The one or morecriteria can include various amplitude criteria, in some instancesevaluated over a certain time period. When a particular gesture isdetected, an operation can be initiated.

This also relates to devices and methods of detecting gestures between afinger of one hand and other body parts (e.g., other fingers or a thumbon the same hand, or the opposing hand) using a device (e.g., a ring) oneach of multiple fingers of the same hand, or on fingers of differenthands. Sense circuitry in each device can be configured to sense asignal at one or more sense electrodes in the device in response todrive signals applied to a drive electrode in each of the devices. Whena particular gesture is detected, an operation can be initiated.

FIGS. 1A-1B illustrate an example system for skin-to-skin contactdetection according to examples of the disclosure. FIG. 1A illustrates asystem including two wrist-worn wearable devices 150A, 150B, eachincluding at least one electrode to establish electrical contact betweenthe wearable device and the wearer's skin. An electrode of a firstwearable device 150A can be used to drive a drive signal (sometimesreferred to as a “stimulation signal”) into the wearer's body via theelectrode's contact with the wrist of right hand 104A. An electrode of asecond wearable device 150B can be used to sense a signal (sometimesreferred to as a “sensed signal” or “received signal”) from the wearer'sbody via contact with the wrist of left hand 104B. As described herein,without contact between hands 104A-104B, a conductive path through thebody can allow for propagation of the drive signal and reception of thesensed signal. Proximity or contact between hands 104A-104B can form asecond conductive path through the contact or proximity for propagationof the drive signal and reception of the sensed signal that can changecharacteristics of the sensed signal. These characteristics can bemonitored and analyzed (e.g., by processing circuitry) and used todetermine whether skin-to-skin contact has been made as discussed inmore detail herein.

In some examples, as illustrated in FIG. 1A, the wearable devices150A-105B can be watches (optionally including crown 162 and/or button164) that can each be fastened to a user via strap 154 or any othersuitable fastener. One or both of the wearable devices 150A-105B caninclude a touch screen 152. It is understood that although wearabledevices 150A-150B are illustrated as including a touch screen 152, thatthe skin-to-skin contact detection can be achieved without a touchscreen or display integrated with wearable devices 150A-150B.Additionally or alternatively, each wearable device can includeprocessing circuitry, drive circuitry sense circuitry, and/or more thanone electrode (e.g., to enable the various drive, sense and processingfunctionalities to be performed by either or both wearable devices). Forexample, FIG. 1B illustrates a backside of wearable device 150 with twoelectrodes 166A-B, though fewer or more electrodes is possible. Forexample, some devices device can include a single electrode (forsingle-ended driving and/or sensing capability), two electrodes (e.g.,for single-ended driving or sensing and/or for differential driving orsensing), three electrodes (e.g., for single-ended driving anddifferential sensing and/or for differential driving and single-endedsensing) or four electrodes (e.g., for differential driving and/ordifferential sensing), etc. It should be understood that each of thewatches can include all of the components above, or that the watches mayinclude fewer components or different components. It should beunderstood that although watches are illustrated in FIGS. 1A-1B thatdifferent devices are possible and/or different placement of the devicesis possible. For example, watches 150A-150B can be replaced with twowristbands; one wristband can include an electrode and drive circuitryand one wristband can include an electrode and sense circuitry. Thecontrol of the drive and sense circuitry and/or the processing of thesignals received by the sense circuitry can be performed by circuitrywithin each respective wristband or by circuitry within another device(e.g., a smartphone or other computing device) based on wired orwireless communication between such a device and the wristbands. In someexamples, one watch may be used for sensing and processing the sensedsignal, and the drive circuitry and electrode can be implemented inanother type of device (e.g., a ring). In some examples, one or bothdevices (e.g., for driving the drive signal and/or sensing the sensedsignal) can be implemented in a glove, finger cuff, bracelet, necklace,head-mounted device, necklace, armband, headphones or ear buds. Althoughprimarily described as wearable devices, in some examples, one or bothdevices can be a non-wearable device such as a handheld controller.Additionally, although primarily described as being implemented in twodevices on two hands, it is understood that in some examples that twodevices can be implement on one hand (e.g., as illustrated in FIGS.7A-7B), and optionally integrated together in one device (e.g., in aglove).

FIG. 2 illustrates a block diagram of an example computing system 200for skin-to-skin contact detection according to examples of thedisclosure. Computing system 200 can include electrodes 202A-202B, sensecircuitry 203, drive circuitry 204 to stimulate first body part withdrive signals and measure sensed signals from a second body part. Insome examples, the drive circuitry can include a voltage source or(constant) current source to generate the stimulation signal. In someexamples, the stimulation signal can have a square waveform. In someexamples, the stimulation signal can have a frequency greater than 500kHz. In some examples, the stimulation signal can be between 1 MHz and10 Mhz. The drive signal can be applied as a single-ended stimulus viaone drive electrode or as a differential signal referenced to a seconddrive electrode (a floating or ground reference). In some examples, thesense circuitry can include an amplifier (with a feedback networkbetween the input(s) and output(s)). In some examples, the amplifier canbe single-ended with the inverting input coupled to the sense electrodeand the non-inverting input coupled to a reference electrode (e.g., aground electrode or a floating electrode). In some examples, theamplifier can be differential with the inverting input coupled to afirst sense electrode and the non-inverting input coupled to a secondsense electrode. A ground electrode can be coupled between the two senseelectrodes. In some examples, the sense circuitry can include multipleamplifiers to sense signals received a multiple sense electrodes (in asingle-ended or differential manner). Additionally, computing system 200can include a digital signal processor (DSP) 206 to analyze and processthe sensed signals for skin-to-skin contact detection (and/or gesturedetection), and optionally memory 207 to store the data from sensecircuitry 203 and/or store configuration data or instructions for DSP206. In some examples, computing system 200 can also include hostprocessor 208, program storage 210 and touch screen 212 (or otherdisplay) to perform display or other operations (e.g., in response toskin-to-skin contact). The components of computing system 200 aredescribed in more detail below.

Host processor 208 can be connected to program storage 210 to executeinstructions stored in program storage 210 (e.g., a non-transitorycomputer-readable storage medium). Host processor 208 can, for example,provide control and data signals to generate a display image on touchscreen 212 (or other display devices), such as a display image of a userinterface (UI). Host processor 208 can also receive outputs from DSP 206(e.g., detection of skin-to-skin contact and/or gestures as touch input)and perform actions based on the outputs (e.g., selection of content orscroll content in a real-world, virtual reality or mixed realityenvironment, etc.). Host processor 208 can also receive outputs (touchinput) from touch screen 212 (or a touch controller, not shown). Theinput (e.g., touch input from touch screen 212 or skin-to-skincontact/gesture input from DSP 206) can be used by computer programsstored in program storage 210 to perform actions. The actions caninclude, but are not limited to, moving an object such as a cursor orpointer, scrolling or panning, adjusting control settings, opening afile or document, viewing a menu, making a selection, executinginstructions, operating a peripheral device connected to the hostdevice, answering a telephone call, placing a telephone call,terminating a telephone call, changing the volume or audio settings,storing information related to telephone communications such asaddresses, frequently dialed numbers, received calls, missed calls,logging onto a computer or a computer network, permitting authorizedindividuals access to restricted areas of the computer or computernetwork, loading a user profile associated with a user's preferredarrangement of the computer desktop, permitting access to web content,launching a particular program, encrypting or decoding a message, and/orthe like. Host processor 208 can also perform additional functions thatmay not be related to touch processing and display.

Note that one or more of the functions described herein, including theanalysis and processing of sensed signals for skin-to-skin contactdetection, can be performed by firmware stored in memory 207 andexecuted by one or more processors (e.g., in DSP 206), or stored inprogram storage 210 and executed by host processor 208. The firmware canalso be stored and/or transported within any non-transitorycomputer-readable storage medium for use by or in connection with aninstruction execution system, apparatus, or device, such as acomputer-based system, processor-containing system, or other system thatcan fetch the instructions from the instruction execution system,apparatus, or device and execute the instructions. In the context ofthis document, a “non-transitory computer-readable storage medium” canbe any medium (excluding signals) that can contain or store the programfor use by or in connection with the instruction execution system,apparatus, or device. The computer-readable storage medium can include,but is not limited to, an electronic, magnetic, optical,electromagnetic, infrared, or semiconductor system, apparatus or device,a portable computer diskette (magnetic), a random access memory (RAM)(magnetic), a read-only memory (ROM) (magnetic), an erasableprogrammable read-only memory (EPROM) (magnetic), a portable opticaldisc such a CD, CD-R, CD-RW, DVD, DVD-R, or DVD-RW, or flash memory suchas compact flash cards, secured digital cards, USB memory devices,memory sticks, and the like.

The firmware can also be propagated within any transport medium for useby or in connection with an instruction execution system, apparatus, ordevice, such as a computer-based system, processor-containing system, orother system that can fetch the instructions from the instructionexecution system, apparatus, or device and execute the instructions. Inthe context of this document, a “transport medium” can be any mediumthat can communicate, propagate or transport the program for use by orin connection with the instruction execution system, apparatus, ordevice. The transport medium can include, but is not limited to, anelectronic, magnetic, optical, electromagnetic or infrared wired orwireless propagation medium.

It is to be understood that the computing system 200 is not limited tothe components and configuration of FIG. 2, but can include other oradditional components (or omit components) in multiple configurationsaccording to various examples. For example, an analog-to-digitalconverter (ADC) may be included as part of the sense circuitry 203 orbetween sense circuitry 203 and DSP 206 to convert the signals to thedigital domain from the analog domain. As another example, touchscreen212 can be omitted and the input information from the analysis andprocessing by DSP 206 can be relayed to another device (e.g., a tablet,laptop, smartphone, computer, server, etc.) via wired or wirelessconnection that can include a display (e.g., a real-world or virtual ormixed reality display). Additionally, the components of computing system200 can be included within a single device, or duplicated in part or inwhole in multiple devices in a system (e.g., as illustrated in anddescribed with reference to FIG. 1A), or can be distributed betweenmultiple devices. In some examples, the drive circuitry 204 and/or sensecircuitry 203 can be in separated from the electrodes such that thedrive/sense circuitry can be implemented in a device worn on the wrist(or a first part of the body, generally) and the electrodes can be wornon or near the fingers (e.g., as part of devices 708A-708B) or palms (ora second different part of the body, generally).

Referring back to sense circuitry 203, sense circuitry 203 can measuresensed signals and can be in communication with DSP 206 to provide thesensed signals to DSP 206. In some examples, the sensed signals can bestored in memory 207 (e.g., acting as a data buffer) and the DSP 206 canacquire a buffered sample of the sensed signal waveform for analysis asdescribed herein. In some examples, memory 207 can be implemented aspart of DSP 206. It should be understood that although a DSP isdescribed, other processing circuits could be used to implement theanalysis and processing described herein including a microprocessor,central processing unit (CPU), programmable logic device (PLD), and/orthe like.

FIGS. 3A-3B illustrate a proximity and a contact, respectively, betweena first body part and a second body part according to examples of thedisclosure. FIGS. 4A-4B illustrate time-domain representations 400, 420and frequency domain representations 402, 422 of the sensed signalcorresponding to the proximity or the contact according to examples ofthe disclosure. With or without contact or proximity, the stimulationgenerated by wearable device 308A (e.g., corresponding to wearabledevice 150, drive circuitry 204 and electrode 202A) can propagatethrough the body via a first path 309A, and can be received by wearabledevice 308B (e.g., corresponding to wearable device 150, sense circuitry203 and electrode 202B). A second path 309B can be formed betweenwearable devices 308A-308B due to contact or proximity between indexfinger 304 and/or right hand 302 and left hand 306. The second path 309Bcan cause changes to the sensed signal when contact or proximity betweenindex finger 304 and hand 306 occurs compared with the expected sensedsignal from first path 309A. FIG. 3A illustrates that a second path 309Bcan be formed between index finger 304 of right hand 302 in proximity tothe palm of left hand 306 (e.g., a capacitive path). FIG. 3B illustratesthat a second path 309B can be formed between index finger 304 of righthand 302 in contact with the palm of left hand 306. The differences inthe sensed waveform can be used to distinguish between skin-to-skintouch and skin-to-skin proximity.

In particular, as shown in FIGS. 4A-4B, the amplitude of a frequencydomain peak (e.g., peak 404 in FIG. 4A and peak 424 in FIG. 4B) canincrease relative to reference peak 414 due to proximity or contact.Thus, an amplitude criterion can be used to detect skin-to-skin contactor proximity. For example, when the peak 404, 424 exceeds a threshold406, 426, the processing circuitry (e.g., DSP 205) can detect contact orproximity. When peak 404, 424 is below the threshold 406, 426, theprocessing circuitry (e.g., DSP 205) can detect an absence of contact orproximity. In some examples, threshold 406 and threshold 426 illustratedin FIGS. 4A-4B can be the same threshold, and one or more additionalcriteria can be used to differentiate between a touch event and aproximity event, as described in more detail below. Although shown asfrequency domain thresholds, it should be understood that time domainthresholds can be used instead for time domain representations 400, 420,in some examples. In some examples, thresholds 406 and 426 can bedifferent thresholds, and can be used to differentiate between a touchevent and a proximity event. For example, the relative amplitudeincrease of peak 404 corresponding to a proximity event can be less thanthe amplitude increase of peak 424 corresponding to a touch event. Afirst, higher threshold can be set to detect a touch event, and asecond, lower threshold can be set to detect a proximity event (e.g.,when the amplitude is less than the first threshold but above the secondthreshold).

Relying on an amplitude criterion alone for differentiation between atouch and hover, however, may be inaccurate (false detection of touchand/or proximity events) because the amplitude may be a function of morethan the distance between the two body parts (the difference betweentouch versus proximity). For example, the capacitive nature of thesecond path 309B for a proximity event (without contact) can result inamplitude changes in the sensed signal that can be a function of thedistance between two body parts (e.g., a distance between left hand 306and index finger 304/right hand 302) and also the size of the body parts(e.g., the size of finger 304 as compared with the hand 302). Likewise,the second path 309B for a contact event can see amplitude changes basedon the size contact, which can change based on the amount of forceapplied or the number of fingers making contact, for example. As aresult, the approach of index finger 304 of right hand 302 and theproximity of right hand 302 and left hand 306 can result in an amplitudespike indicative of contact based on the amplitude threshold beforeindex finger 304 makes contact with left hand 306. This can cause afalse detection of contact (e.g., detecting contact while the fingerhovers), and even if contact occurs subsequently, the amplitude spikecan mask the contact of index finger 304 (because the subsequentamplitude change may be a relatively small change compared with theproximity of the larger hands). Additionally, the timing of the momentof contact (even if it can be differentiated from proximity) may beimprecise.

As described herein, one or more additional criteria can be used toimprove skin-to-skin contact or proximity detection. The one or moreadditional criteria can be related to other characteristics of thesensed signal. In some examples, the one or more additional criteria cancorrespond to whether the sensed signal has a distorted waveform or not.For example, time domain representation 400 corresponding to a proximityevent can include distortion compared with the time domainrepresentation corresponding to a touch event. The waveform can appearmore similar to a saw-tooth waveform (distorted in FIG. 4A) than a sinewaveform (non-distorted in FIG. 4B).

In some examples, the sensed signal can be correlated with a referencewaveform. For example, a reference waveform can be a sine waveformcorresponding to the sensed signal without contact or proximity events.For example, FIG. 5 illustrates a block diagram of a correlation circuit500 according to examples of the disclosure. Correlator 502 ofcorrelation circuit 500 can receive the sensed signal as a first inputand a reference signal as a second signal, and can output a correlationof the input signals. The sensed signal can be provided by sensecircuitry 203 directly or from storage in memory 207, for example. Thereference signal can be stored in memory 207. Correlator 502 can beimplemented, in some examples, in DSP 206. When the correlation is high(above a threshold) between the sensed signal and the referencewaveform, the processing circuitry (e.g., DSP 206) can determine thatthe signal has a non-distorted waveform and/or detect a skin-to-skincontact event. When the correlation is low (below the threshold) betweenthe sensed signal and the reference waveform, the processing circuitry(e.g., DSP 206) can determine that the signal has a distorted waveformand/or detect a proximity event (without contact). In some examples, thereference waveform can be a saw-tooth waveform, and the conventions canbe reversed with respect to the threshold (e.g., high correlationcorresponds to distortion/proximity and low correlation corresponds tocontact). It should be understood that the sensed signal and referencesignal waveforms illustrated correspond to a square wave stimulationapplied to the body. However, a different stimulation signal, sensedsignal, and reference signal can be used in other examples. Althoughdescribed as a correlation of the time domain representations,correlation can also be performed on frequency domain representations.

In some examples, a second criterion can be based on the width of afrequency domain peak. The width of the peak 404, 424 (W₁, W₂respectively) in the frequency domain can provide an indication ofdistortion. For example, a frequency domain representation of a puresine wave at one frequency can be spike at that frequency. The narrowerthe width of the peak, the closer the sensed signal is to a sine wave.Thus, a width threshold can be used to determine whether the sensedsignal is distorted or non-distorted based on how the width of the peakcompares with the width threshold. When the width of peak 404, 424 isbelow the threshold, the processing circuitry (e.g., DSP 206) candetermine that the signal has a non-distorted waveform and/or detect askin-to-skin contact event. When the width of peak 404, 424 is above thethreshold, the processing circuitry (e.g., DSP 206) can determine thatthe signal has a distorted waveform and/or detect a proximity event(without contact).

In some examples, the width of the peak can be measured at a fixed point(e.g., at a fixed amplitude point). For example, the width can bemeasured at the amplitude threshold 406, 426, or at another fixed point.In some examples, the width measurement can be normalized according tothe amplitude of the peak (because peaks may widen as the amplitudeincreases). The amplitude-normalized width of the peak can be used withthe amplitude-normalized width threshold in a similar manner asdescribed above. In some examples, the width can be measured at amidpoint of the amplitude of the peak. In some examples, theamplitude-normalized width can be a ratio of the width at a fixedamplitude point to the maximum amplitude at the peak (e.g., scaledaccording to maximum amplitude) that can be compared to anamplitude-normalized width threshold.

In some examples, a second criterion can be based on an envelope of thesensed signal. As illustrated in FIG. 4A, time domain representation 400of the sensed signal includes an envelope 401 when a proximity eventoccurs, whereas as illustrated in FIG. 4B the envelope can beessentially flattened when a contact event occurs. In some examples, theenvelope can appear as a second, low-frequency peak 408 (relative topeak 404) in the frequency domain representation 402. When the amplitudeof the second peak 408 is above a second amplitude threshold 412(different and lower than amplitude threshold 406), the processingcircuitry (e.g., DSP 206) can determine that the signal has a distortedwaveform and/or detect a proximity event (without contact). When thesecond peak 408 is below threshold 412 (or non-existent), the processingcircuitry (e.g., DSP 206) can determine that the signal has anon-distorted waveform and/or detect a skin-to-skin contact event.Although described as frequency domain processing to identify theexistence of the envelope in a beat frequency, alternatively processingcan be performed in the time domain using the time domain representationof the envelope with a threshold based on the flatness of the envelopefunction.

In some examples, the second criterion can be based on a phase shiftbetween the stimulation signal and the sensed signal. For example, inaddition to receiving the sensed signal, the processing circuitry (e.g.,DSP 206) can also receive the drive signal. The processing circuitry cancalculate the phase shift. Thus, a phase shift threshold can be used todetermine whether the sensed signal is distorted or non-distorted basedon how the calculated phase shift compares with the phase shiftthreshold. In some examples, when the phase shift is below thethreshold, the processing circuitry (e.g., DSP 206) can determine thatthe signal has a non-distorted waveform and/or detect a skin-to-skincontact event. When the phase shift is above the threshold, theprocessing circuitry (e.g., DSP 206) can determine that the signal has adistorted waveform and/or detect a proximity event (without contact).

In some examples, the one or more criteria can include a thirdcriterion. For example, when hands are within the field of view of acamera or cameras (not shown in FIG. 2), processing circuitry canreceive an input stream from the camera(s) and can estimate whether acontact or proximity event occurs using the camera input. In someexamples, the camera may provide useful information about the size,position and orientation of the body parts, which may used todifferentiate between an amplitude spike caused by large objects inproximity (e.g., two parallel palms) versus contact between two smallerobjects (e.g., two finger tips). However, it is understood that thedetection of and differentiation between skin-to-skin contact events andproximity events can be performed even without the use of a camera.Detection without the camera(s) may be particularly advantageous whenone or both hands are out of the field of view of the camera(s) or oneof the hands occludes the other of the hands (making optical detectionof whether objects are touching or in proximity difficult).

FIG. 6 illustrates an example process 600 of skin-to-skin contactdetection according to examples of the disclosure. At 605, a sensedsignal can be measured at a sense electrode (e.g., in contact with afirst body part) in response to a drive signal applied by a driveelectrode (e.g., in contact with a second body part, different from thefirst body part). In some examples, the drive signal can be a squarewave with a frequency greater than 500 kHz. In some examples, the drivesignal can be a square wave with a frequency between 1 MHz and 10 MHz.The sensed signal can be processed to detect skin-to-skin contactbetween two body parts. In some examples, the processing can includetransforming the sensed signal from a time domain to a frequency domain(e.g., using a fast Fourier transform (FFT) or other suitabletechnique). In some examples, the processing can be performed entirelyin the time domain without transforming the sensed signal to thefrequency domain. The processing can include, at 610, detecting contactbetween the first body part and the second body part in accordance witha determination that one or more criteria are met. The one or morecriteria can include a first criterion that is met when an amplitude ofthe sensed signal exceeds an amplitude threshold (615). For example,determining whether the amplitude of the sensed signal exceeds theamplitude threshold for evaluating the first criterion can includecomparing a peak identified in the frequency domain with the amplitudethreshold (620). The one or more criteria can include a second criterionthat is met when the sensed signal has a non-distorted waveform (625).Evaluating the second criterion can include, in some examples, comparinga width (in some examples an amplitude-normalized width) of the peakidentified in the frequency domain with a width threshold (630). Inaccordance with a determination that the width is below the widththreshold, determining that the sensed signal has the non-distortedwaveform (the second criterion is met); and in accordance with adetermination that the width is above the width threshold, determiningthat the sensed signal has a distorted waveform (the second criterion isnot met). Evaluating the second criterion can include, in some examples,comparing a second, low-frequency peak identified in the frequencydomain with a second amplitude threshold (635). In accordance with adetermination that an amplitude of the second peak is below the secondamplitude threshold (or in the absence of a second peak at the lowerfrequency), the processing circuitry can determine that the sensedsignal has the non-distorted waveform (the second criterion is met). Inaccordance with a determination that the amplitude of the second peak isabove the second amplitude threshold, the processing circuitry candetermine that the sensed signal has a distorted waveform (the secondcriterion is not met). Evaluating the second criterion can include, insome examples, correlating the sensed signal with a reference signal(640). In accordance with a determination that the correlation is abovea correlation threshold, determining that the sensed signal has thenon-distorted waveform (the second criterion is met); and in accordancewith a determination that the correlation is below the correlationthreshold, determining that the sensed signal has a distorted waveform(the second criterion is not met). Process 600 can include, at 645,detecting no contact between the first body part and the second bodypart in accordance with a determination that the one or more criteriaare not met. Process 600 can include, at 650, detecting a proximitywithout contact between the first body part and the second body part inaccordance with a determination that first criterion is met and that thesecond criterion is not met.

It is understood that process 600 is an example process and that some ofthe processing mentioned above can be omitted or different processingmay be performed. For example, the second criterion can be evaluatedusing processing of 630, 635 or 640. In some examples, the secondcriterion can met when multiple characteristics indicate non-distortionof the waveform (e.g., using processing of 630, 635 and/or 640).

In some examples, in addition to detecting skin-to-skin contact,skin-to-skin gestures can be detected as well. For example, the gesturesenabled by skin-to-skin contact can include a tap, double tap,tap-and-hold (long press) and the like. In additional, otherskin-to-skin contact gestures can be enabled based on movementsubsequent to contact. For example, a sliding gesture can be detectedbased on skin-to-skin contact followed on-skin movement (e.g., prior tobreaking skin-to-skin contact). In some examples, the skin-to-skincontact can be between two fingers on the same hand and the slidinggesture can be one finger sliding along a second finger on the samehand.

FIGS. 7A-7B illustrate an example system for detection of a skin-to-skingesture according to examples of the disclosure. In particular, FIGS.7A-7B illustrate a slide gesture between a first finger and a secondfinger of the same hand according to examples of the disclosure. Thesystem can use a computing system including the same or similarcomponents as described with reference to computing system 200. FIGS.8A-8C illustrate time-domain representations 800, 810 and 820 andfrequency domain representations 802, 812, 822 of the sensed signalcorresponding to a finger-to-finger slide gesture according to examplesof the disclosure. As illustrated in FIGS. 7A-7B, a first wearabledevice 708A (e.g., corresponding to wearable device 150, drive circuitry204 and electrode 202A) can be coupled on a first finger, thumb 702, anda second wearable device 708B (e.g., corresponding to wearable device150, sense circuitry 203 and electrode 202B) can be coupled on a secondfinger, index finger 704. In some examples, the first wearable device708A can be disposed at or near (within a threshold distance of) themidpoint of thumb 702 (e.g., at or near the boundary between the distalbone and the proximal bone). In some examples, the first wearable device708A can be disposed at or near (within a threshold distance of) thebase of thumb 702 (e.g., at or near the base of the metacarpal bone). Insome examples, the second wearable device 708B can be disposed at ornear (within a threshold distance of) the base of index finger 704(e.g., at or near the base of the metacarpal bone). In some examples,the first wearable device 708A can be finger cuff and the secondwearable device 708B can be a ring. In some examples, the first andsecond wearable devices can be implemented as part of a glove.

With or without the contact between thumb 702 and index finger 704 shownin FIGS. 7A-7B, the stimulation generated by wearable device 708A canpropagate through the body via a first path 709A, and can be received bywearable device 708B. A second path 709B can be formed between wearabledevices 708A-708B due to contact between thumb 702 and index finger 704.The second path 709B can cause changes to the sensed signal comparedwith the expected sensed signal from first path 709A when contactbetween thumb 702 and index finger 704 occurs. The changes to the sensedsignal can be different depending upon the location of thumb 702 onindex finger 704. In particular, the closer the tip of thumb 702 is tothe tip of index finger 704, the higher the resistance of the secondpath and the lower the resulting amplitude spike due to contact. In asimilar manner, the closer the tip of thumb 702 is to the base of indexfinger 704 (and wearable device 708B), the lower the resistance of thesecond path and the larger the resulting amplitude spike due to contact.The changes in the sensed waveform (e.g., the difference in amplitudespike) can be used to identify movement of the contact location betweenthe two fingers to identify a gesture (e.g., a slide gesture).

The detection of a movement gesture can include the detection of contactbetween the first finger and the second finger (e.g., thumb 702 andindex finger 704) and the detection of movement of the first fingeralong the second finger. The skin-to-skin contact of thumb 702 and indexfinger 704 can be detected via the one or more criteria (e.g., includingan amplitude criterion and a non-distortion criterion) as discussedabove and not repeated here for brevity. The movement of the contact canbe detected by an increase or decrease in amplitude of the sensed signal(relative to the initial amplitude at contact) while skin-to-skincontact is maintained.

FIG. 8A, for example, shows a frequency domain peak 806 corresponding toan initial contact (e.g., corresponding to the position of the fingersshown in FIG. 7A). FIGS. 8B and 8C show the corresponding frequencydomain peaks corresponding to a subsequent contact. FIG. 8B, forexample, shows a frequency domain peak 816 corresponding to a subsequentcontact with a decreased amplitude peak indicative of movement away fromthe base of the finger (e.g., away from wearable device 708B). FIG. 8C,for example, shows a frequency domain peak 826 corresponding to asubsequent contact with an increased amplitude peak, indicative ofmovement toward the base of the finger (e.g., toward from wearabledevice 708B, corresponding to the position of the fingers shown in FIG.7B). Detection of movement away from the base of the finger cancorrespond to a slide-away gesture, and detection of movement toward thebase of the finger can correspond to a slide-toward gesture. Theslide-away and slide-toward gestures can provide different inputs to asystem. In some examples, the opposite directions of the slide inputscan correspond to opposite functionality (e.g., raising vs. loweringvolume, moving a slider control in opposite directions, etc.). Althoughshown as frequency domain peaks, it should be understood that changes ofamplitude in the time domain can be used instead for detection ofmovement and determining a direction of sliding.

In some examples, in order to detect a slide gesture, the amount ofmovement must be a threshold amount of movement in order to avoid falsepositives when a change in amplitude detected may due to other reasonsother than a change in position (e.g., movement). For example, the otherreasons may include a change in the size of the contact (e.g., byadding/removing fingers, pressing with more/less force with the finger,or changing the orientation of the finger) or adding moisture.Additionally or alternatively to requiring a threshold amount ofmovement to identify a movement gesture, in some examples, informationfrom another sensor can be used to exclude these external causes. Forexample, camera(s) or other optical sensor(s), a force sensor ormoisture sensor can be used to exclude other causes of the change in theamplitude of the finger. For example, camera(s)/optical sensor(s) can beused to exclude the change in number of fingers or the orientation orforce of the finger. A force sensor can be used to exclude the change inapplied force. A moisture sensor can be used to exclude a change inmoisture.

Additionally or alternatively, in some examples, one or more additionalsense electrodes and corresponding sense circuitry can be used to recordmultiple measurements along a finger (e.g., along index finger 704). Forexample, an additional sense electrode and/or sense circuitry can belocated at or near the distal bone of index finger 704 in addition tothe electrode and/or sense circuitry at or near the base of themetacarpal bone of index finger 704. In some examples, the slide ofthumb 702 can be detected based on both the increase in the sensedsignal at one sense electrode and the decrease in the sensed signal atthe other sense electrode (or visa versa). In some examples, adifferential measurement of the signal sensed from the two senseelectrodes can be taken and the increase or decrease in the differentialsensed signal can be used to detect a slide gesture. Such a differentialmeasurement can improve rejection of alternative sources of signalamplitude change that may be common mode. For example, the change inamplitude due to applied force can appear as common mode at both senseelectrodes and thus may be removed by a differential measurement(thereby reducing false positive detection of force as a gesture). It isunderstood that the differential measurement can provide a similarbenefit to reducing false positives in skin-to-skin contact detection asdescribed herein (e.g., not limited to reducing false positives forgesture detection).

Although movement gestures are described herein primarily with respectto finger-to-finger gestures, it should be understood that gestures maybe detected using other body parts. For example, using the wearabledevices of FIGS. 3A-3B, a sliding gesture may be detected of one fingeron one hand sliding along a second finger of the other hand.Additionally or alternatively, a sliding gesture may be detected of onefinger along a palm of the other hand. In some examples, multiple senseelectrodes (and corresponding sensing circuitry) can be located atdifferent parts of the palm. For example, as shown in FIG. 3B, foursensing electrodes 350A-350D can be disposed at approximately fourcorners of the palm (e.g., in a glove for example) and can be sensedwith corresponding sensing circuitry (e.g., co-located or locatedelsewhere, such as on the backside of the palm or in wearable device308B). Based on the relative changes in amplitude at the multiple senseelectrodes, the processing circuitry can determine relative movement ofthe index finger 304. As a result, multiple directional slide gesturescan be enabled (e.g., slide up, slide down, slide left, slide right,diagonal slides, etc.). The sensed signals may be differential betweensense electrodes to reduce common mode changes to signal amplitude dueto applied force as described above.

FIG. 9 illustrates an example process 900 of skin-to-skin gesturedetection according to examples of the disclosure. At 905, a sensedsignal can be measured at a sense electrode (e.g., in contact with afinger of a hand) in response to a drive signal applied by a driveelectrode (e.g., in contact with a different finger of the same hand).In some examples, the drive signal can be a square wave with a frequencygreater than 500 kHz. In some examples, the drive signal can be a squarewave with a frequency between 1 MHz and 10 MHz. At 910, the sensedsignal can be processed to detect a skin-to-skin contact gesture inaccordance with a determination that one or more criteria are met. Insome examples, the processing can include, at 915, detectingskin-to-skin contact between the two fingers in accordance with adetermination that one or more contact criteria are met (e.g., asdescribed above with respect to process 900, and not repeated here forbrevity). The processing can include, at 920, detecting movement of afirst finger along a second finger. Detecting movement of the firstfinger along the second finger can be based on an increase or decreasein amplitude of the sensed signal subsequent to and while contact ismade between the first and second fingers (925). In some examples, theincrease or decrease in amplitude (relative to the initial amplitudeupon contact) can be based on the time domain sensed signal. In someexamples, the increase or decrease in amplitude can be based on thefrequency domain sensed signal (e.g., such that the processing mayinclude a frequency domain transformation). An increase in amplitudefrom an initial amplitude upon contact can be indicative of aslide-toward gesture. A decrease in amplitude from the initial amplitudeupon contact can be indicative of a slide-away gesture. In someexamples, to reduce false positive detection of a gesture, that athreshold amount of increase or decrease in amplitude may be required(corresponding to a threshold amount of movement) to detect a gesture.In some examples, to reduce false positive detection of a gesture, anadditional sensor may be used to exclude another source of the increaseor decrease (e.g., a camera, force sensor, etc.). At 930, in accordancewith a determination that the one or more criteria are not met, theprocessing circuitry (e.g., DSP 206) can forgo detecting the movementgesture. It is understood that process 900 is an example and that someof the processing mentioned above can be omitted or different processingmay be performed.

Although examples of the disclosure presented above utilize at least twoseparate devices, including one device to generate a drive signal andanother device to receive a sense signal, in other examples a singledevice (e.g., a ring) can be used to both generate a drive signal andreceive a sense signal to detect contact and/or movement gesturesbetween a finger of one hand and other body parts (e.g., other fingersor a thumb on the same hand, or the opposing hand). For example, asingle device can detect a same-hand index finger and thumb touch (pinchor tap), an index finger and middle finger touch (pinch or tap), anindex finger and middle finger touch followed by the addition of thethumb, an index finger and thumb touch followed by the addition of themiddle finger, an index finger touching or tapping an opposite hand, orthe thumb sliding along the index finger, and other gesture inputs.These gesture inputs can be detected and advantageously used to initiateoperations using a single unobtrusive device, such as a ring, that maybe commonly worn by a user for AR/VR and smart home operations. In stillother examples, multiple devices, each capable of generating a differentstimulation frequency and receiving a sense signal, can be utilized tounambiguously detect a finger touching an opposite hand, detect fingerpinches using the thumb and multiple fingers of the same hand performedat different times or simultaneously, or detect gestures performed ontwo hands at different times or simultaneously.

FIG. 10 illustrates wearable device 1002 in the form of a ring accordingto examples of the disclosure. In the example of FIG. 10, wearabledevice 1002 can include band mechanism 1018 electrically coupled toelectronic jewel system (jewel) 1020, although in other examples thejewel may be integrated within the band mechanism. Band mechanism 1018can include ground electrode 1008, drive electrode 1010, anddifferential sense electrodes 1012 and 1014. In some examples, theseelectrodes can be wrapped fully or almost entirely around thecircumference of band mechanism 1018. In other examples, the electrodescan be discrete electrode patches.

FIG. 11 is a system block diagram of wearable device 1102 according toexamples of the disclosure. In the example of FIG. 11, which maycorrespond to device 1002 in FIG. 10, band mechanism 1118 can beelectrically coupled to jewel 1120 through connections 1122, which insome examples can be so-called “pogo pins,” which are spring-loadedelectrical connectors that press into, and make electrical contact with,conductive areas (lands or targets). Band mechanism 1118 can includeground electrode 1108, drive electrode 1110, and sense electrodes 1112and 1114.

Jewel 1120 can include controller 1124 coupled to memory and/or storage1126. Controller 1124 may correspond to DSP 206 described above andshown in FIG. 2, and can include one or more processors capable ofexecuting programs stored in memory 1126 to perform various functions.In some examples of the disclosure, controller 1124 can be connected towireless transmitter or transceiver 1128 and one or more of inertialmeasurement unit (IMU) 1130 and haptics generator 1168. Memory 1126 maycorrespond to memory 207 and/or program storage 210 described above andshown in FIG. 2, and can include, but is not limited to, random accessmemory (RAM) or other types of memory or storage, watchdog timers andthe like. In some examples, controller 1124 can include drive circuitry1132 configured for applying a stimulation signal to drive electrode1110, and/or sense circuitry 1134 configured for sensing signals onsense electrodes 1112 and 1114. Drive circuitry 1132 and sense circuitry1134 may correspond to drive circuitry 204 and sense circuitry 203described above and shown in FIG. 2, respectively. In some examples,drive circuitry 1132 can be separate from controller 1124 include afrequency source or generator, an amplifier, a pulse-width modulator(PWM) or the like for generating a stimulation signal. In some examples,the stimulation signal can be in the range of about 100 kHz to 10 MHz,because higher frequencies can pass more easily through the capacitivenature of a user's body. In some examples, the stimulation signal can bein the range of 3.3V, which can be advantageously provided directly fromsome microcontrollers without the need for level shifters. In someexamples, sense circuitry 1134 can be separate from controller 1124, andcan include an instrumentation amplifier that can perform differentialsensing across two inputs, each coupled to a different sense electrode1112 and 1114. In some examples, sensing can be performed at about 5megasamples per second (MS/s). Controller 1124 can also becommunicatively coupled to IMU 1130 to process signals from the IMU todetermine parameters such as the angular rate, orientation, position,and velocity of wearable device 1102. In some examples, controller 1124can be communicatively coupled to haptics generator 1168 to initiatehaptic feedback. Controller 1124 can also be communicatively coupled towireless transmitter or transceiver 1128 to wirelessly send and receivedata and other information. In some examples, wireless transmitter ortransceiver 1128 can communicate wirelessly with desktop, laptop andtablet computing devices, smartphones, media players, other wearablessuch as watches and health monitoring devices, smart home control andentertainment devices, headphones and ear buds, and devices forcomputer-generated environments such as augmented reality, mixedreality, or virtual reality environments, and the like.

It should be apparent that the architecture shown in FIG. 11 is only oneexample architecture of band mechanism 1118 and jewel 1120, and that thesystem could have more or fewer components than shown, or a differentconfiguration of components. For example, some of the processing ofjewel 1120 can be offloaded to separate devices such as those mentionedabove, and the jewel can contain reduced controller functionality alongwith wireless transceiver 1128 to enable communication with thoseseparate devices. Regardless of where they are located, the variouscomponents shown in FIG. 11 can be implemented in hardware, software,firmware or any combination thereof, including one or more signalprocessing and/or application specific integrated circuits.

FIG. 12A illustrates hand 1200 with index finger 1204 supportingwearable device (e.g., ring) 1202 but not making contact with thumb 1206according to examples of the disclosure. Although the example of FIG.12A shows device 1202 worn over index finger 1204, it should beunderstood that in other examples device 1202 can be worn over otherfingers such as middle finger 1216, or over thumb 1206. Device 1202 caninclude ground electrode 1208, drive electrode 1210, differential senseelectrodes 1212 and 1214, and other electronics not shown in FIG. 12A.The order of ground electrode 1208, drive electrode 1210, anddifferential sense electrodes 1212 and 1214 need not be as shown in theexample of FIG. 12A, and in other examples the order of electrodes canbe rearranged. In addition, in other examples a single-ended senseelectrode can be utilized instead of differential sense electrodes 1212and 1214.

FIG. 12B illustrates the hand of FIG. 12A, except that index finger 1204is now making contact with thumb 1206 according to examples of thedisclosure.

FIG. 12C illustrates sense output signal 1236 detected at device 1202when index finger 1204 and thumb 1206 make and break contact as shown inFIGS. 12B and 12A according to examples of the disclosure. In theexample of FIG. 12C, sense output signal 1236 can be derived from anoutput of an instrumentation amplifier or other circuitry in device1202. For example, raw differential sense signals can be received atsense electrodes 1212 and 1214, and sense output signal 1236 can be aselected peak of a Fast Fourier Transform (FFT) of the raw differentialsense signals over time. In other examples, as an alternative to the FFTsignal processing described above, an envelope of the raw differentialsignals can be captured over time. The amplitude modulated (AM) rawdifferential sense signals can be high-pass or band-pass filtered usinga filter tuned to the stimulation signal frequency to remove RFfrequencies that can distort the envelope. The filtered signals can thenbe rectified (e.g., using a rectifier circuit) and passed through anenvelope detector (e.g., using an envelope detector circuit) to produceoutput signal 1236 without RF components. If multiple stimulation signalfrequencies are employed, tuned filters, rectification and envelopedetection can be separately performed at each frequency. Sense outputsignal 1236 can represent a “signature” of index finger 1204 coming intocontact with thumb 1206, and therefore detection of this signature canenable device 1202 to determine that an input gesture comprised of anindex finger and thumb pinch has been received.

At time t1, index finger 1204 and thumb 1206 are not touching (the“break contact” condition as shown in FIG. 12A), and a stimulationsignal generated at drive electrode 1210 can propagate through indexfinger 1204 to differential sense electrodes 1212 and 1214, producingvoltage v1 on sense output signal 1236. At time t2, index finger 1204and thumb 1206 contact each other (the “make contact” condition as shownin FIG. 12B), which can provide grounding path 1238 between senseelectrode 1214 and ground electrode 1208 through the thumb. Groundingpath 1238 can result in a greater voltage difference betweendifferential sense electrodes 1212 and 1214, which can cause a resultantdrop in the amplitude of sense output signal 1236 to v2. It should benoted that if thumb 1206 does not contact index finger 1204 but insteadcontacts the middle, ring or pinky fingers, grounding path 1238 wouldnot exist and no voltage drop to v2 would occur. At time t4, indexfinger 1204 and thumb 1206 separate (break contact), and becausegrounding path 1238 is no longer present, sense output signal 1236returns to v1.

In some examples, circuitry within device 1202 (e.g., ananalog-to-digital converter (ADC) or other circuitry) can be used tocapture voltage levels and determine when the sense output is above,below or within various voltage thresholds, such as above voltagethreshold vth1 or below voltage threshold vth2. However, because voltagelevels by themselves may not be sufficient to unambiguously identify asignature and determine that a particular gesture has occurred, in someexamples time durations can also be monitored. Time durations can bedetermined and monitored using timing circuits and/or algorithms withindevice 1102 to evaluate signal transition times, shapes, durations, etc.For example, at time periods t2 and t4, sense output signal 1236 can beevaluated to confirm that it transitions between expected voltage levelsor crosses expected voltage thresholds within a certain time period(i.e., to detect expected steep transitions in the sense output signalas compared to gradual increases or decreases indicative of otherbehavior).

In the example of FIG. 12C, when sense output signal 1236 is determinedto be above vth1 at time t1, a timer can be started (e.g., clock cyclescan be counted, a capacitance can be charged, etc.) to confirm that thesense output signal remains above vth1 for a first time period (e.g.,until time t2), which can indicate a steady state “break” conditionwhere index finger 1204 is not touching any other finger or thumb. Attime t2, when sense output signal 1236 drops from v1 to v2, it can bedetermined whether the sense output signal has fallen with a requisitesteepness. When the voltage level is confirmed to have dropped belowvth2 with a requisite steepness, it can then be determined how long thesense output signal stays below voltage threshold vth2. In one example,when the sense output signal falls below voltage threshold vth2 with acertain steepness and stays below voltage threshold vth2 for a secondtime period until at least time t3, it can be determined that an indexfinger 1204 and thumb 1206 contact (e.g., an index finger-thumb pinch)has occurred. When sense output signal 1236 returns to a voltage levelabove voltage threshold vth1 at time t4 with a requisite steepness andstays at that level for a third time period (e.g., to time t5), it canbe determined that index finger 1204 and thumb 1206 have separated andreturned to the steady state condition.

In some examples, the single device 1202 can be utilized to detect aslide gesture. For example, if thumb 1206 contacts index finger 1204near the tip of the index finger, a certain voltage drop at sense outputsignal 1236 can be produced (e.g., a voltage drop to a level belowvth2). However, if thumb 1206 contacts index finger at a location closerto device 1202, a reduced voltage drop can be produced on sense outputsignal 1236 (but still below vth2 in the example of FIG. 12C). Thus, forexample, if thumb 1206 initially touches the tip of index finger 1204,then slides along the index finger towards device 1202, the voltage atsense output signal 1236 may initially be at v2, but increase towardsvth2 as the thumb slides towards the device. In some examples, differentvoltages at sense output signal 1236 can be mapped to differentlocations along index finger 1204, or voltage changes at the senseoutput can be converted to relative slide distances. In other examples,capturing the voltage level of sense output signal 1236 over time canallow for a determination of slide velocity or acceleration. These slidedetection parameters can be used as control inputs for variousoperations.

Although FIG. 12C illustrates a voltage drop when index finger 1204contacts thumb 1206, in other examples the amplitude of sense outputsignal 1236 may rise when the index finger contacts the thumb. Ingeneral, for the example of FIG. 12C and any of the subsequentlydisclosed examples, the direction and amount of change in the senseoutput signal for a given gesture can be a function of the order inwhich the sense electrodes are arranged, and/or the configuration of thesense circuit within the device. Thus, it should be understood that thevoltage levels and the direction of voltage changes described andillustrated herein are for purposes of illustration only, and that inother examples the voltage levels can be different, and signals can be“inverted.” Accordingly, for example, a voltage above first voltagethreshold vth1 can be said to “satisfy” that threshold in FIG. 12C, butif FIG. 12C were inverted due to a different circuit configuration, avoltage below vth1 can also be said to “satisfy” that threshold.

FIG. 13A illustrates hand 1300 with index finger 1304 supportingwearable device (e.g., ring) 1302 but not making contact with middlefinger 1316 according to examples of the disclosure. Device 1302 caninclude ground electrode 1308, drive electrode 1310, differential senseelectrodes 1312 and 1314, and other electronics not shown in FIG. 13A.The order of ground electrode 1308, drive electrode 1310, anddifferential sense electrodes 1312 and 1314 need not be as shown in theexample of FIG. 13A, and in other examples the order of electrodes canbe rearranged. In addition, in other examples a single-ended senseelectrode can be utilized instead of differential sense electrodes 1312and 1314.

FIG. 13B illustrates the hand of FIG. 13A, except that index finger 1304is now making contact with middle finger 1316 according to examples ofthe disclosure.

FIG. 13C illustrates sense output signal 1344 detected at device 1302when index finger 1304 and middle finger 1316 make and break contact asshown in FIGS. 13B and 13A according to examples of the disclosure. Inthe example of FIG. 13C, sense output signal 1344 can be derived from anoutput of an instrumentation amplifier or other circuitry in device1302. For example, raw differential sense signals can be received atsense electrodes 1312 and 1314, and sense output signal 1344 can be aselected peak of an FFT of the raw differential sense signals over time.Alternatively, filtering, rectification and envelope detection asdescribed above can also be used to generate sense output signal 1344.Sense output signal 1344 can represent a “signature” of index finger1304 coming into contact with middle finger 1316, and thereforedetection of this signature can enable device 1302 to determine that aninput gesture comprised of an index finger coming into contact with amiddle finger has been received.

At time t1, index finger 1304 and middle finger 1316 are not touching(the “break contact” condition as shown in FIG. 13A), and a stimulationsignal generated at drive electrode 1310 can propagate through indexfinger 1304 to differential sense electrodes 1312 and 1314, producingvoltage v1 on sense output signal 1344. At time t2, index finger 1304and middle finger 1316 contact each other (the “make contact” conditionas shown in FIG. 13B), which can provide grounding path 1340 betweensense electrode 1314 and ground electrode 1308 through the middlefinger. Grounding path 1340 can result in a greater voltage differencebetween differential sense electrodes 1312 and 1314, which can cause aresultant drop in the amplitude of sense output signal 1344 to v2. Aftertime t2, sense output signal 1344 can gradually increase over time inwhat can appear to be a roughly logarithmic curve until time t4, whenindex finger 1304 and middle finger 1316 separate (break contact). Insome examples, this gradual voltage increase can be caused by a gradualincrease in moisture between index finger 1304 and middle finger 1316.In other examples, this gradual voltage increase can be caused by agradual increase in resistance or impedance between index finger 1304and middle finger 1316. At time t4, after a temporary downward voltagespike at 1342, the amplitude of sense output signal 1344 returns to v1because grounding path 1340 is no longer present.

In some examples, circuitry within device 1302 (e.g., an ADC or othercircuitry) can be used to capture voltage levels and determine when thesense output is above, below or within various voltage thresholds, suchas above voltage threshold vth1 or below voltage threshold vth2.However, because voltage levels by themselves may not be sufficient tounambiguously identify a signature and determine that a particulargesture has occurred, in some examples time durations can also bemonitored. Time durations can be determined and monitored using timingcircuits and/or algorithms within device 1302 to evaluate signaltransition times, shapes, durations, etc.

In the example of FIG. 13C, when sense output signal 1344 is determinedto be above vth1 at time t1, a timer can be started (e.g., clock cyclescan be counted, a capacitance can be charged, etc.) to confirm that thesense output signal remains above vth1 for a first time period (e.g.,until time t2), which can indicate a steady state “break” conditionwhere index finger 1304 is not touching any other finger or thumb. Attime t2, when sense output signal 1344 drops from v1 to v2, it can bedetermined whether the sense output signal has fallen with a requisitesteepness. When the voltage level is confirmed to have dropped belowvth2 with a requisite steepness, it can then be determined how long thesense output signal stays below voltage threshold vth2. In one example,when the sense output falls below voltage threshold vth2 with arequisite steepness, but only for a second time period less than thetime from t2 to t3, it can be determined that index finger 1304 andmiddle finger 1316 contact has occurred. When sense output signal 1344returns to a voltage level above voltage threshold vth1 at time t4 witha requisite steepness and stays at that level for a third time period,it can be determined that index finger 1304 and middle finger 1316 haveseparated and returned to the steady state condition.

FIG. 14A illustrates hand 1400 with index finger 1404 supportingwearable device (e.g., ring) 1402 and in contact with middle finger 1416according to examples of the disclosure. Device 1402 can include groundelectrode 1408, drive electrode 1410, differential sense electrodes 1412and 1414, and other electronics not shown in FIG. 14A. Grounding path1440 can be generated between sense electrode 1414 and ground electrode1408 through middle finger 1416. The order of ground electrode 1408,drive electrode 1410, differential sense electrodes 1412 and 1414 neednot be as shown in the example of FIG. 14A, and in other examples theorder of electrodes can be rearranged. In addition, in other examples asingle-ended sense electrode can be utilized instead of differentialsense electrodes 1412 and 1414.

FIG. 14B illustrates the hand of FIG. 14A, except that thumb 1406 is nowmaking contact with already touching index finger 1404 and middle finger1416 according to examples of the disclosure. Grounding path 1448 can beformed between sense electrode 1414 and ground electrode 1408 throughthumb 1406.

FIG. 14C illustrates sense output signal 1446 detected at device 1402when thumb 1406 makes and breaks contact with already touching indexfinger 1404 and middle finger 1416 according to examples of thedisclosure. In the example of FIG. 14C, sense output signal 1446 can bederived from an output of an instrumentation amplifier or othercircuitry in device 1402. For example, raw differential sense signalscan be received at sense electrodes 1412 and 1414, and sense outputsignal 1446 can be a selected peak of an FFT of the raw differentialsense signals over time. Alternatively, filtering, rectification andenvelope detection as described above can also be used to generate senseoutput signal 1446. Sense output signal 1446 can represent a “signature”of thumb 1406 coming into contact with already touching index finger1404 and middle finger 1416, and therefore detection of this signaturecan enable device 1402 to determine that an input gesture comprised of athumb coming into contact with already touching index and middle fingershas been received.

At time t1, index finger 1404 and middle finger 1416 are not touching(as shown in FIG. 13A), and a stimulation signal generated at driveelectrode 1410 can propagate through index finger 1404 to differentialsense electrodes 1412 and 1414, producing voltage v1 on sense outputsignal 1446. At time t2, index finger 1404 and middle finger 1416contact each other (as shown in FIG. 14A), which can provide groundingpath 1440 between sense electrode 1414 and ground electrode 1408 throughthe middle finger. Grounding path 1440 (hidden in FIG. 14B) can resultin a greater voltage difference between differential sense electrodes1412 and 1414, which can cause a resultant drop in the amplitude ofsense output signal 1446 to v2. After time t2, sense output signal 1446can increase over time in what can appear to be a roughly logarithmiccurve until time t4, when thumb 1406 comes into contact with touchingindex finger 1404 and middle finger 1416.

At time t4, with thumb 1406 now in contact with touching index finger1404 and middle finger 1416, an abrupt rise in the amplitude of senseoutput signal 1466 to v3 (above vth3) can occur, where v3 can be greaterthan v1. At time t5, thumb 1406 can separate from touching index finger1404 and middle finger 1416, resulting in sense output signal 1446returning to a voltage level between vth1 and vth2.

In some examples, circuitry within device 1402 (e.g., ADC or othercircuitry) can be used to capture voltage levels and determine when thesense output is above, below or within various voltage thresholds vth1,vth2 or vth3. However, because voltage levels by themselves may not besufficient to unambiguously identify a signature and determine that aparticular gesture has occurred, in some examples time durations canalso be monitored. Time durations can be determined and monitored usingtiming circuits and/or algorithms within device 1402 to evaluate signaltransition times, shapes, durations, etc.

In the example of FIG. 14C, when sense output signal 1446 is determinedto be above vth1 at time t1, a timer can be started (e.g., clock cyclescan be counted, a capacitance can be charged, etc.) to confirm that thesense output signal remains above vth1 for a first time period (e.g.,until time t2), which can indicate a steady state “break” conditionwhere index finger 1404 is not touching any other finger or thumb. Attime t2, when sense output signal 1446 drops from v1 to v2, it can bedetermined whether the sense output signal has fallen with a requisitesteepness. When the voltage level is confirmed to have fallen belowvoltage threshold vth2 with a requisite steepness, it can then bedetermined how long the sense output signal stays below voltagethreshold vth2. In one example, when the amplitude of sense outputsignal 1446 falls below voltage threshold vth2 with a requisitesteepness, but only for a second timer period less than the time from t2to t3, it can be determined that index finger 1404 and middle finger1416 contact has occurred. While sense output signal 1446 is betweenvth1 and vth2 (indicative of touching index finger 1404 and middlefinger 1416), if the amplitude of sense output signal 1446 then rises attime t4 with a requisite steepness to a voltage v3 such that it exceedsvoltage threshold vth3, it can further be determined that thumb 1406 hasbeen added to the touching index and middle fingers. If sense outputsignal 1446 then drops back down at time t5 to between vth1 and vth2with a requisite steepness, it can further be determined that thumb 1406has broken contact with touching index finger 1404 and middle finger1406.

FIG. 15A illustrates hand 1500 with index finger 1504 supportingwearable device (e.g., ring) 1502 and making contact with thumb 1506according to examples of the disclosure. Device 1502 can include groundelectrode 1508, drive electrode 1510, differential sense electrodes 1512and 1514, and other electronics not shown in FIG. 15A. The order ofground electrode 1508, drive electrode 1510, differential senseelectrodes 1512 and 1514 need not be as shown in the example of FIG.15A, and in other examples the order of electrodes can be rearranged. Inaddition, in other examples a single-ended sense electrode can beutilized instead of differential sense electrodes 1512 and 1514.

FIG. 15B illustrates the hand of FIG. 15A, except that middle finger1516 is now making contact with already touching index finger 1504 andthumb 1506 according to examples of the disclosure.

FIG. 15C illustrates sense output signal 1550 detected at device 1502when middle finger 1516 makes and breaks contact with already touchingindex finger 1504 and thumb 1506 according to examples of thedisclosure. In the example of FIG. 15C, sense output signal 1550 can bederived from an output of an instrumentation amplifier or othercircuitry in device 1502. For example, raw differential sense signalscan be received at sense electrodes 1512 and 1514, and sense outputsignal 1550 can be a selected peak of an FFT of the raw differentialsense signals over time. Alternatively, filtering, rectification andenvelope detection as described above can also be used to generate senseoutput signal 1550. Sense output signal 1550 can represent a “signature”of middle finger 1516 coming into contact with already touching indexfinger 1504 and thumb 1506, and therefore detection of this signaturecan enable device 1502 to determine that an input gesture comprised of amiddle finger coming into contact with already touching index finger andthumb has been received.

At time t1, index finger 1504 and thumb 1506 are not touching, and astimulation signal generated at drive electrode 1510 can propagatethrough index finger 1504 to differential sense electrodes 1512 and1514, producing voltage v1 on sense output signal 1550 at the output ofthe sense circuitry in device 1502. At time t2, index finger 1504 andthumb 1506 contact each other (as shown in FIG. 15A), which can providegrounding path 1538 between sense electrode 1514 and ground electrode1508 through the thumb. Grounding path 1538 can result in a greatervoltage difference between differential sense electrodes 1512 and 1514,which can cause a resultant drop in the amplitude of sense output signal1550 to v2. At time t3, middle finger 1516 can come into contact withtouching index finger 1504 and thumb 1506, and an abrupt rise in theamplitude of sense output signal 1550 to v3 can occur. At time t4,middle finger 1516 can separate from touching index finger 1504 andthumb 1506, resulting in the amplitude of sense output signal 1550returning to a voltage level less than vth2.

In some examples, circuitry within device 1502 (e.g., ADC or othercircuitry) can be used to capture voltage levels and determine when thesense output is above, below or between any of voltage thresholds vth1,vth2 or vth3. However, because voltage levels by themselves may not besufficient to unambiguously identify a signature and determine that aparticular gesture has occurred, in some examples time durations canalso be monitored.

In the example of FIG. 15C, when sense output signal 1550 is determinedto be above vth1 and time t1, a timer can be started (e.g., clock cyclescan be counted, a capacitance can be charged, etc.) to confirm that thesense output signal remains above vth1 for a first time period (e.g.,until time t2), which can indicate a steady state “break” conditionwhere index finger 1504 is not touching any other finger or thumb. Attime t2, when sense output signal 1550 drops from v1 to v2, it can bedetermined whether the sense output signal has fallen with a requisitesteepness. When the voltage level is confirmed to have dropped belowvoltage threshold vth2 with a requisite steepness, it can then bedetermined how long the sense output stays below voltage threshold vth2.In one example, when the sense output signal falls below voltagethreshold vth2 with a certain steepness and stays below voltagethreshold vth2 for a second time period until at least time t3, it canbe determined that an index finger 1504 and thumb 1506 contact (e.g., anindex finger-thumb pinch) has occurred. At time t4, middle finger 1516can come into contact with touching index finger 1504 and thumb 1506,and an abrupt rise in sense output signal 1550 to v3 (greater than v1)can occur. At time t5, middle finger 1516 can separate from touchingindex finger 1504 and thumb 1506, resulting in the amplitude of senseoutput signal 1550 returning to a voltage level less than vth2.

FIG. 16A illustrates hand 1600 with index finger 1604 supportingwearable device (e.g., ring) 1602 and making contact with opposite hand1652 according to examples of the disclosure. Although the example ofFIG. 16A shows device 1602 over index finger 1604, it should beunderstood that in other examples device 1602 can be worn over otherfingers such as middle finger 1616. Device 1602 can include groundelectrode 1608, drive electrode 1610, differential sense electrodes 1612and 1614, and other electronics not shown in FIG. 16A. The order ofground electrode 1608, drive electrode 1610, differential senseelectrodes 1612 and 1614 need not be as shown in the example of FIG.16A, and in other examples the order of electrodes can be rearranged. Inaddition, in other examples a single-ended sense electrode can beutilized instead of differential sense electrodes 1612 and 1614.

Although index finger 1604 in the example of FIG. 16A is not touchingthumb 1606 (as in FIG. 12B), nevertheless the sense output signal“signature” can be similar to that shown in FIG. 12C, because a similargrounding path 1654 (similar to grounding path 1238 in FIG. 12B) can bepresent between sense electrode 1614 and ground electrode 1608 via theuser's body. Accordingly, in some examples a separate camera can beemployed to distinguish between the gesture of FIG. 12B and the gestureof FIG. 16A.

FIG. 16B illustrates left hand 1600 with index finger supportingwearable device (e.g., ring) 1602A and also right hand 1652 with indexfinger 1656 supporting wearable device (e.g., ring) 1602B according toexamples of the disclosure. Although the example of FIG. 16B showsdevice 1602A over index finger 1604 of left hand 1600, and device 1602Bover index finger 1656 of right hand 1652, it should be understood thatin other examples the devices can be worn over other fingers on the leftand right hands. Having devices 1602A and 1602B on both hands can enablea user to provide the gesture inputs described above with either hand,either separately or simultaneously.

In addition, in some examples, the stimulation frequency applied to thedrive electrode of device 1602A can be different from the stimulationfrequency applied to the drive electrode of device 1602B. By providingdifferent stimulation frequencies on devices 1602A and 1602B, theambiguity presented by receiving a similar output waveform “signature”from the index finger-thumb gesture of FIG. 12B and also the indexfinger-opposite hand gesture of FIG. 16A can be resolved withoutrequiring a camera. For example, if device 1602A generates a 5 MHzstimulation signal and device 1602B generates an 8 MHz stimulationsignal, then an index finger-thumb input gesture generated by device1602A on left hand 1600 can produce the sense output signature of FIG.12C at 5 MHz at device 1602A. However, if index finger 1604 of left hand1600 touches right hand 1652, the 8 MHz stimulation signal generated bydevice 1602B of the right hand can couple onto device 1602A of the lefthand, and the sense output signal at device 1602A can be a compositesignal having both 5 MHz and 8 MHz components. These frequencycomponents can be separately detected to unambiguously determine thatindex finger 1604 of left hand 1600 is touching right hand 1652 (ratherthan left thumb 1606).

FIG. 16C illustrates hand 1600 with index finger 1604 supportingwearable device (e.g., ring) 1602A and middle finger 1616 supportingwearable device (e.g., ring) 1602B according to examples of thedisclosure. Wearing devices on two fingers of the same hand can allow auser to perform additional input gestures using a single hand, such as amiddle finger-thumb pinch gesture similar to the index finger-thumbpinch gesture of FIGS. 12A-12C. Although FIG. 16C shows devices on indexfinger 1604 and middle finger 1616, in other examples devices can beworn on any combination of index, middle, ring, and pinky fingers toprovide additional input gesture possibilities.

FIG. 17 illustrates a flowchart for detecting input gestures using oneor more devices according to examples of the disclosure. In the exampleof FIG. 17, at block 1758 one or more devices can be worn on one or morefingers of one or both hands. At block 1760, each device can generate astimulation signal at a different frequency. At block 1762, sense outputsignal amplitudes can be captured at each device over time. At block1764, the amplitudes of sense output signals can be compared to variousvoltage and time thresholds/windows to identify an input gesturesignature and the gesture being performed. At block 1766, differentoperations can be initiated, controlled or performed based on theidentified gesture.

Therefore, according to the above, some examples of the disclosure aredirected to a system. The system can comprise sense circuitry andprocessing circuitry. The sense circuitry can be coupled to a senseelectrode, the sense circuitry configured to sense a signal at the senseelectrode in response to a drive signal applied to a first body part.The sense electrode can be configured to contact a second body part,different from the first body part. The processing circuitry can beconfigured to: in accordance with a determination that one or morecriteria are met, detect contact between the first body part and thesecond body part; and in accordance with a determination that the one ormore criteria are not met, detect no contact between the first body partand the second body part. The one or more criteria can include a firstcriterion that is met when an amplitude of the sensed signal exceeds anamplitude threshold and a second criterion that is met when the sensedsignal has a non-distorted waveform. Additionally or alternatively toone or more of the examples disclosed above, in some examples, theprocessing circuitry can be further configured to: in accordance with adetermination that the first criteria is met and that the secondcriterion is not met, detecting proximity of the first body part to thesecond body part without contact between the first body part and thesecond body part. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, the system can furthercomprise: drive circuitry coupled to a drive electrode. The drivecircuitry can be configured to apply the drive signal to the driveelectrode, and the drive electrode can be configured to contact thefirst body part. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, determining whether theamplitude of the sensed signal exceeds the amplitude threshold cancomprise identifying a peak in a frequency domain representation of thesensed signal and comparing the peak identified in the frequency domainwith the amplitude threshold in the frequency domain. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, determining whether the sensed signal has a non-distortedwaveform can comprise comparing a width of the peak identified in thefrequency domain with a width threshold. In accordance with adetermination that the width is below the width threshold, determiningthat the sensed signal has the non-distorted waveform; and in accordancewith a determination that the width is above the width threshold,determining that the sensed signal has a distorted waveform.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, determining whether the sensed signal has anon-distorted waveform can comprise comparing an amplitude-normalizedwidth of the peak identified in the frequency domain with a widththreshold. In accordance with a determination that theamplitude-normalized width is below the width threshold, determiningthat the sensed signal has the non-distorted waveform; and in accordancewith a determination that the amplitude-normalized width is above thewidth threshold, determining that the sensed signal has a distortedwaveform. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, determining whether the receivedsensed has a non-distorted waveform can comprise identifying a secondpeak in the frequency domain representation of the sensed signal, thesecond peak at a lower frequency than the first peak, and comparing thesecond peak identified in the frequency domain with a second amplitudethreshold in the frequency domain. In accordance with a determinationthat an amplitude of the second peak is below the second amplitudethreshold, determining that the sensed signal has the non-distortedwaveform; and in accordance with a determination that the amplitude ofthe second peak is above the second amplitude threshold, determiningthat the sensed signal has a distorted waveform. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, determining whether the sensed signal has a non-distortedwaveform can comprise correlating the sensed signal with a referencesignal. In accordance with a determination that the correlation is abovea correlation threshold, determining that the sensed signal has thenon-distorted waveform; and in accordance with a determination that thecorrelation is below the correlation threshold, determining that thesensed signal has a distorted waveform. Additionally or alternatively toone or more of the examples disclosed above, in some examples, the drivesignal can have a frequency greater than 500 kHz or between 1-10 MHz.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the drive signal can be a square wave.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the first body part can comprise a first wristand hand and the second body part can comprise a second wrist and hand.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, detecting contact between the first body partand the second body part can comprise detecting contact between a fingerof a first hand and a palm or a finger of a second hand.

Some examples of the disclosure are directed to a method. The method cancomprise: at a device comprising sense circuitry and processingcircuitry: sensing, via sense circuitry, a signal at a sense electrodeconfigured to contact a first body part, in response to a drive signalapplied by a drive electrode configured to contact a second body part,different from the first body part; and in accordance with adetermination that one or more criteria are met, detecting contactbetween the first body part and the second body part; and in accordancewith a determination that the one or more criteria are not met,detecting no contact between the first body part and the second bodypart. The one or more criteria can include a first criterion that is metwhen an amplitude of the sensed signal exceeds an amplitude thresholdand a second criterion that is met when the sensed signal has anon-distorted waveform. Additionally or alternatively to one or more ofthe examples disclosed above, in some examples, the method can furthercomprise: in accordance with a determination that the first criteria ismet and that the second criterion is not met, detecting proximity of thefirst body part to the second body part without contact between thefirst body part and the second body part. Additionally or alternativelyto one or more of the examples disclosed above, in some examples,determining whether the amplitude of the sensed signal exceeds theamplitude threshold can comprise identifying a peak in a frequencydomain representation of the sensed signal and comparing the peakidentified in the frequency domain with the amplitude threshold in thefrequency domain. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, determining whether thesensed signal has a non-distorted waveform can comprise comparing awidth of the peak identified in the frequency domain with a widththreshold. In accordance with a determination that the width is belowthe width threshold, determining that the sensed signal has thenon-distorted waveform; and in accordance with a determination that thewidth is above the width threshold, determining that the sensed signalhas a distorted waveform. Additionally or alternatively to one or moreof the examples disclosed above, in some examples, determining whetherthe sensed signal has a non-distorted waveform can comprise comparing anamplitude-normalized width of the peak identified in the frequencydomain with a width threshold. In accordance with a determination thatthe amplitude-normalized width is below the width threshold, determiningthat the sensed signal has the non-distorted waveform; and in accordancewith a determination that the amplitude-normalized width is above thewidth threshold, determining that the sensed signal has a distortedwaveform. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, determining whether the receivedsensed has a non-distorted waveform can comprise identifying a secondpeak in the frequency domain representation of the sensed signal, thesecond peak at a lower frequency than the first peak, and comparing thesecond peak identified in the frequency domain with a second amplitudethreshold in the frequency domain. In accordance with a determinationthat an amplitude of the second peak is below the second amplitudethreshold, determining that the sensed signal has the non-distortedwaveform; and in accordance with a determination that the amplitude ofthe second peak is above the second amplitude threshold, determiningthat the sensed signal has a distorted waveform. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, determining whether the sensed signal has a non-distortedwaveform can comprise correlating the sensed signal with a referencesignal. In accordance with a determination that the correlation is abovea correlation threshold, determining that the sensed signal has thenon-distorted waveform; and in accordance with a determination that thecorrelation is below the correlation threshold, determining that thesensed signal has a distorted waveform. Additionally or alternatively toone or more of the examples disclosed above, in some examples, the drivesignal can have a frequency greater than 500 kHz or between 1-10 MHz.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the drive signal can be a square wave.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the first body part can comprise a first wristand hand and the second body part can comprise a second wrist and hand.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, detecting contact between the first body partand the second body part can comprise detecting contact between a fingerof a first hand and a palm or a finger of a second hand. Some examplesof the disclosure are directed to a non-transitory computer readablestorage medium. The non-transitory computer readable storage medium canstore instructions (e.g., one or more programs), which when executed byone or more processors of an electronic device, can cause the electronicdevice to perform any of the above methods.

Some examples of the disclosure are directed to a system. The system cancomprise sense circuitry and processing circuitry. The sense circuitrycan be coupled to a sense electrode, the sense circuitry configured tosense a signal at the sense electrode in response to a drive signalapplied to a first finger of a hand, and the sense electrode configuredto contact a second finger of the hand, different from the first finger.The processing circuitry can be configured to: in accordance with adetermination that one or more criteria are met, detect a movementgesture; and in accordance with a determination that the one or morecriteria are not met, forgo detecting the movement gesture. The one ormore criteria can include a first criterion indicative of contactbetween the first finger and the second finger and a second criterionindicative of movement of the first finger along the second finger.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the first criterion can be met when anamplitude of the sensed signal exceeds an amplitude threshold.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the first criterion can be met when anamplitude of the sensed signal exceeds an amplitude threshold and whenthe sensed signal has a non-distorted waveform. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, the second criterion can be met when an amplitude of thesensed signal increases or decreases by a threshold amount subsequent toand while the first criterion is met. Additionally or alternatively toone or more of the examples disclosed above, in some examples, themovement gesture can be a slide gesture. Additionally or alternativelyto one or more of the examples disclosed above, in some examples, inaccordance with a determination that an amplitude of the sensed signalincreases from an initial value (by a threshold amount), the detectedmovement gesture can be a slide-toward gesture. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, in accordance with a determination that an amplitude of thesensed signal decreases from an initial value (by a threshold amount),the detected movement gesture can be a slide-away gesture. Additionallyor alternatively to one or more of the examples disclosed above, in someexamples, the first electrode can be configured to contact the firstfinger at or near the base of the first finger and the second electrodecan be configured to contact the second finger at or near the base ofthe second finger. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, the first finger can be athumb and the second finger can be an index finger. The first electrodecan be configured to contact the first finger at or near the middle ofthe thumb, and the second electrode can be configured to contact theindex finger at or near the base of the index finger.

Some examples of the disclosure are directed to a method. The method cancomprise: at a device comprising sense circuitry and processingcircuitry: sensing, via sense circuitry, a signal at a sense electrodein response to a drive signal applied by a drive electrode configured tocontact a first finger of a hand, the sense electrode configured tocontract a second finger of the hand, different from the first finger;and in accordance with a determination that one or more criteria aremet, detect a movement gesture; and in accordance with a determinationthat the one or more criteria are not met, forgo detecting the movementgesture. The one or more criteria can include a first criterionindicative of contact between the first finger and the second finger anda second criterion indicative of movement of the first finger along thesecond finger. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, the first criterion can bemet when an amplitude of the sensed signal exceeds an amplitudethreshold. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, the first criterion can be met whenan amplitude of the sensed signal exceeds an amplitude threshold andwhen the sensed signal has a non-distorted waveform. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, the second criterion can be met when an amplitude of thesensed signal increases or decreases by a threshold amount subsequent toand while the first criterion is met. Additionally or alternatively toone or more of the examples disclosed above, in some examples, themovement gesture can be a slide gesture. Additionally or alternativelyto one or more of the examples disclosed above, in some examples, inaccordance with a determination that an amplitude of the sensed signalincreases from an initial value (by a threshold amount), the detectedmovement gesture can be a slide-toward gesture. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, in accordance with a determination that an amplitude of thesensed signal decreases from an initial value (by a threshold amount),the detected movement gesture can be a slide-away gesture. Additionallyor alternatively to one or more of the examples disclosed above, in someexamples, the first electrode can be configured to contact the firstfinger at or near the base of the first finger and the second electrodecan be configured to contact the second finger at or near the base ofthe second finger. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, the first finger can be athumb and the second finger can be an index finger. The first electrodecan be configured to contact the first finger at or near the middle ofthe thumb, and the second electrode can be configured to contact theindex finger at or near the base of the index finger. Some examples ofthe disclosure are directed to a non-transitory computer readablestorage medium. The non-transitory computer readable storage medium canstore instructions (e.g., one or more programs), which when executed byone or more processors of an electronic device, can cause the electronicdevice to perform any of the above methods.

Some examples of the disclosure are directed to a wearable device fordetecting gestures, comprising drive circuitry coupled to a driveelectrode and configured to generate a stimulation signal, the driveelectrode positioned at a first location in the device for contacting afirst finger of a first hand, sense circuitry coupled to at least onesense electrode and configured to generate a sense output signal basedon one or more sense signals received at the at least one senseelectrode in response to the stimulation signal, the at least one senseelectrode positioned at a second location in the device for contactingthe first finger of the first hand, and a processor communicativelycoupled to the drive and sense circuitry and configured for capturing anamplitude of the sense output signal over time, and in accordance with adetermination that a first set of amplitude and time criteria are met,detecting a making of contact of the first finger with an adjacentsecond finger of the first hand. Additionally or alternatively to one ormore of the examples disclosed above, in some examples the processor isfurther configured for, in accordance with a determination that a secondset of amplitude and time criteria are met following the determinationthat the first set of amplitude and time criteria are met, detecting abreaking of contact of the first finger and the adjacent second finger.Additionally or alternatively to one or more of the examples disclosedabove, in some examples the processor is further configured for, inaccordance with a determination that a second set of amplitude and timecriteria are met following the determination that the first set ofamplitude and time criteria are met, detecting a making of contact of athumb of the first hand with the touching first and second fingers.Additionally or alternatively to one or more of the examples disclosedabove, in some examples the processor is further configured for, inaccordance with a determination that a third set of amplitude and timecriteria are met following the determination that the second set ofamplitude and time criteria are met, detecting a breaking of contact ofthe thumb of the first hand with the touching first finger and secondfingers. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples the determination that the first setof amplitude and time criteria are met comprises determining that thesense output signal satisfies a first voltage threshold during a firsttime period between a first time and a second time, determining that thesense output signal changes to satisfy a second voltage threshold at thesecond time, determining that the sense output signal changes andapproaches the second voltage threshold while continuing to satisfy thesecond voltage threshold during a portion of a second time periodbetween the second time and a third time, and determining that the senseoutput signal no longer satisfies the second voltage threshold at thethird time. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples the processor is further configuredfor, in accordance with a determination that a second set of amplitudeand time criteria are met following the determination that the first setof amplitude and time criteria are met, detecting a breaking of contactof the first finger and the adjacent second finger, wherein thedetermination that the second set of amplitude and time criteria are metcomprises determining that the sense output signal changes to satisfythe first voltage threshold at a fourth time. Additionally oralternatively to one or more of the examples disclosed above, in someexamples the processor is further configured for, in accordance with adetermination that a second set of amplitude and time criteria are metfollowing the determination that the first set of amplitude and timecriteria are met, detecting a making of contact of a thumb of the firsthand with the touching first and second fingers, wherein thedetermination that the second set of amplitude and time criteria are metcomprises determining that the sense output signal changes to satisfy athird voltage threshold at a fourth time. Additionally or alternativelyto one or more of the examples disclosed above, in some examples theprocessor is further configured for, in accordance with a determinationthat a third set of amplitude and time criteria are met following thedetermination that the second set of amplitude and time criteria aremet, detecting a breaking of contact of the thumb and the touching firstfinger and second fingers, wherein the determination that the third setof amplitude and time criteria are met comprises determining that thesense output signal changes to a voltage between the first voltagethreshold and the second voltage threshold at a fifth time. Additionallyor alternatively to one or more of the examples disclosed above, in someexamples the at least one sense electrode comprises two differentialsense electrodes, and the device further comprises a ground electrodepositioned at a third location in the device for contacting the firstfinger of the first hand, wherein the ground electrode, the driveelectrode, and the two differential sense electrodes are arranged inorder in the device.

Some examples of the disclosure are directed to a method for detectinggestures, the method performed at a wearable device including drivecircuitry, sense circuitry, and processing circuitry, the methodcomprising generating a stimulation signal for propagating through afirst finger of a first hand, generating a sense output signal based onone or more sense signals received from the first finger of the firsthand in response to the stimulation signal, capturing an amplitude ofthe sense output signal over time, and in accordance with adetermination that a first set of amplitude and time criteria are met,detecting a making of contact of the first finger with an adjacentsecond finger of the first hand. Additionally or alternatively to one ormore of the examples disclosed above, in some examples the methodfurther comprises, in accordance with a determination that a second setof amplitude and time criteria are met following the determination thatthe first set of amplitude and time criteria are met, detecting abreaking of contact of the first finger and the adjacent second finger.Additionally or alternatively to one or more of the examples disclosedabove, in some examples the method further comprises, in accordance witha determination that a second set of amplitude and time criteria are metfollowing the determination that the first set of amplitude and timecriteria are met, detecting a making of contact of a thumb of the firsthand with the touching first and second fingers. Additionally oralternatively to one or more of the examples disclosed above, in someexamples the method further comprises, in accordance with adetermination that a third set of amplitude and time criteria are metfollowing the determination that the second set of amplitude and timecriteria are met, detecting a breaking of contact of the thumb of thefirst hand and the touching first finger and second fingers.Additionally or alternatively to one or more of the examples disclosedabove, in some examples the determination that the first set ofamplitude and time criteria are met comprises determining that the senseoutput signal satisfies a first voltage threshold during a first timeperiod between a first time and a second time, determining that thesense output signal changes to satisfy a second voltage threshold at thesecond time, determining that the sense output signal changes andapproaches the second voltage threshold while continuing to satisfy thesecond voltage threshold during a portion of a second time periodbetween the second time and a third time, and determining that the senseoutput signal no longer satisfies the second voltage threshold at thethird time. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples the method further comprises, inaccordance with a determination that a second set of amplitude and timecriteria are met following the determination that the first set ofamplitude and time criteria are met, detecting a breaking of contact ofthe first finger and the adjacent second finger, wherein thedetermination that the second set of amplitude and time criteria are metcomprises determining that the sense output signal changes to satisfythe first voltage threshold at a fourth time. Additionally oralternatively to one or more of the examples disclosed above, in someexamples the method further comprises, in accordance with adetermination that a second set of amplitude and time criteria are metfollowing the determination that the first set of amplitude and timecriteria are met, detecting a making of contact of a thumb of the firsthand with the touching first and second fingers, wherein thedetermination that the second set of amplitude and time criteria are metcomprises determining that the sense output signal changes to satisfy athird voltage threshold at a fourth time. Additionally or alternativelyto one or more of the examples disclosed above, in some examples themethod further comprises, in accordance with a determination that athird set of amplitude and time criteria are met following thedetermination that the second set of amplitude and time criteria aremet, detecting a breaking of contact of the thumb and the touching firstfinger and second fingers, wherein the determination that the third setof amplitude and time criteria are met comprises determining that thesense output signal changes to a voltage between the first voltagethreshold and the second voltage threshold at a fifth time.

Some examples of the disclosure are directed to a wearable device fordetecting gestures, comprising drive circuitry coupled to a driveelectrode and configured to generate a stimulation signal, the driveelectrode positioned at a first location in the device for contacting afirst finger of a first hand, sense circuitry coupled to at least onesense electrode and configured to generate a sense output signal basedon one or more sense signals received at the at least one senseelectrode in response to the stimulation signal, the at least one senseelectrode positioned at a second location in the device for contactingthe first finger of the first hand, and a processor communicativelycoupled to the drive and sense circuitry and configured for capturing anamplitude of the sense output signal over time, in accordance with adetermination that a first set of amplitude and time criteria are met,detecting a making of contact of the first finger with a thumb of thefirst hand, and in accordance with a determination that a second set ofamplitude and time criteria are met following the determination that thefirst set of amplitude and time criteria are met, detecting a making ofcontact of a second finger adjacent to the first finger of the firsthand with the touching first finger and thumb. Additionally oralternatively to one or more of the examples disclosed above, in someexamples the processor is further configured for, in accordance with adetermination that a third set of amplitude and time criteria are metfollowing the determination that the second set of amplitude and timecriteria are met, detecting a breaking of contact of the second fingerwith the touching first finger and thumb.

Some examples of the disclosure are directed to a method for detectinggestures, the method performed at a wearable device including drivecircuitry, sense circuitry, and processing circuitry, the methodcomprising generating a stimulation signal for propagating through afirst finger of a first hand, generating a sense output signal based onone or more sense signals received from the first finger of the firsthand in response to the stimulation signal, capturing an amplitude ofthe sense output signal over time, in accordance with a determinationthat a first set of amplitude and time criteria are met, detecting amaking of contact of the first finger with a thumb of the first hand,and in accordance with a determination that a second set of amplitudeand time criteria are met following the determination that the first setof amplitude and time criteria are met, detecting a making of contact ofa second finger adjacent to the first finger of the first hand with thetouching first finger and thumb.

Although examples of this disclosure have been fully described withreference to the accompanying drawings, it is to be noted that variouschanges and modifications will become apparent to those skilled in theart. Such changes and modifications are to be understood as beingincluded within the scope of examples of this disclosure as defined bythe appended claims.

The invention claimed is:
 1. A wearable device for detecting gestures,comprising: drive circuitry coupled to a drive electrode and configuredto generate a stimulation signal, the drive electrode positioned at afirst location in the device for contacting a first finger of a firsthand; sense circuitry coupled to at least one sense electrode andconfigured to generate a sense output signal based on one or more sensesignals received at the at least one sense electrode in response to thestimulation signal, the at least one sense electrode positioned at asecond location in the device for contacting the first finger of thefirst hand; and a processor communicatively coupled to the drive andsense circuitry and configured for capturing an amplitude of the senseoutput signal over time, and in accordance with a determination that afirst set of amplitude and time criteria are met, detecting a making ofcontact of the first finger with a second finger adjacent to the firstfinger of the first hand.
 2. The device of claim 1, the processorfurther configured for: in accordance with a determination that a secondset of amplitude and time criteria are met following the determinationthat the first set of amplitude and time criteria are met, detecting abreaking of contact of the first finger and the second finger.
 3. Thedevice of claim 1, the processor further configured for: in accordancewith a determination that a second set of amplitude and time criteriaare met following the determination that the first set of amplitude andtime criteria are met, detecting a making of contact of a thumb of thefirst hand with the first finger or the second finger while the firstfinger and the second finger are making contact.
 4. The device of claim3, the processor further configured for: in accordance with adetermination that a third set of amplitude and time criteria are metfollowing the determination that the second set of amplitude and timecriteria are met, detecting a breaking of contact of the thumb of thefirst hand with the first finger and the second finger while the firstfinger and the second finger are making contact.
 5. The device of claim1, wherein the determination that the first set of amplitude and timecriteria are met comprises: determining that the sense output signalsatisfies a first voltage threshold during a first time period between afirst time and a second time; determining that the sense output signalchanges to satisfy a second voltage threshold at the second time;determining that the sense output signal changes and approaches thesecond voltage threshold while continuing to satisfy the second voltagethreshold during a portion of a second time period between the secondtime and a third time; and determining that the sense output signal nolonger satisfies the second voltage threshold at the third time.
 6. Thedevice of claim 5, the processor further configured for: in accordancewith a determination that a second set of amplitude and time criteriaare met following the determination that the first set of amplitude andtime criteria are met, detecting a breaking of contact of the firstfinger and the second finger; wherein the determination that the secondset of amplitude and time criteria are met comprises determining thatthe sense output signal changes to satisfy the first voltage thresholdat a fourth time.
 7. The device of claim 5, the processor furtherconfigured for: in accordance with a determination that a second set ofamplitude and time criteria are met following the determination that thefirst set of amplitude and time criteria are met, detecting a making ofcontact of a thumb of the first hand with the first finger or the secondfinger while the first finger and the second finger are making contact;wherein the determination that the second set of amplitude and timecriteria are met comprises determining that the sense output signalchanges to satisfy a third voltage threshold at a fourth time.
 8. Thedevice of claim 7, the processor configured for: in accordance with adetermination that a third set of amplitude and time criteria are metfollowing the determination that the second set of amplitude and timecriteria are met, detecting a breaking of contact of the thumb and thefirst finger and the second finger while the first finger and the secondfinger are making contact; wherein the determination that the third setof amplitude and time criteria are met comprises determining that thesense output signal changes to a voltage between the first voltagethreshold and the second voltage threshold at a fifth time.
 9. Thedevice of claim 1, wherein the at least one sense electrode comprisestwo differential sense electrodes, the device further comprising: aground electrode positioned at a third location in the device forcontacting the first finger of the first hand; wherein the groundelectrode, the drive electrode, and the two differential senseelectrodes are arranged in order in the device.
 10. A method fordetecting gestures, the method performed at a wearable device includingdrive circuitry, sense circuitry, and processing circuitry, the methodcomprising: generating a stimulation signal for propagating through afirst finger of a first hand; generating a sense output signal based onone or more sense signals received from the first finger of the firsthand in response to the stimulation signal; capturing an amplitude ofthe sense output signal over time; and in accordance with adetermination that a first set of amplitude and time criteria are met,detecting a making of contact of the first finger with a second fingeradjacent to the first finger of the first hand.
 11. The method of claim10, further comprising: in accordance with a determination that a secondset of amplitude and time criteria are met following the determinationthat the first set of amplitude and time criteria are met, detecting abreaking of contact of the first finger and the second finger.
 12. Themethod of claim 10, further comprising: in accordance with adetermination that a second set of amplitude and time criteria are metfollowing the determination that the first set of amplitude and timecriteria are met, detecting a making of contact of a thumb of the firsthand with the first finger or the second finger while the first fingerand the second finger are making contact.
 13. The method of claim 12,further comprising: in accordance with a determination that a third setof amplitude and time criteria are met following the determination thatthe second set of amplitude and time criteria are met, detecting abreaking of contact of the thumb of the first hand and the first fingerand the second finger while the first finger and the second finger aremaking contact.
 14. The method of claim 10, wherein the determinationthat the first set of amplitude and time criteria are met comprises:determining that the sense output signal satisfies a first voltagethreshold during a first time period between a first time and a secondtime; determining that the sense output signal changes to satisfy asecond voltage threshold at the second time; determining that the senseoutput signal changes and approaches the second voltage threshold whilecontinuing to satisfy the second voltage threshold during a portion of asecond time period between the second time and a third time; anddetermining that the sense output signal no longer satisfies the secondvoltage threshold at the third time.
 15. The method of claim 14, furthercomprising: in accordance with a determination that a second set ofamplitude and time criteria are met following the determination that thefirst set of amplitude and time criteria are met, detecting a breakingof contact of the first finger and the second finger; wherein thedetermination that the second set of amplitude and time criteria are metcomprises determining that the sense output signal changes to satisfythe first voltage threshold at a fourth time.
 16. The method of claim14, further comprising: in accordance with a determination that a secondset of amplitude and time criteria are met following the determinationthat the first set of amplitude and time criteria are met, detecting amaking of contact of a thumb of the first hand with the first finger orthe second finger while the first finger and the second finger aremaking contact; wherein the determination that the second set ofamplitude and time criteria are met comprises determining that the senseoutput signal changes to satisfy a third voltage threshold at a fourthtime.
 17. The method of claim 16, further comprising: in accordance witha determination that a third set of amplitude and time criteria are metfollowing the determination that the second set of amplitude and timecriteria are met, detecting a breaking of contact of the thumb and thefirst finger and the second finger while the first finger and the secondfinger are making contact; wherein the determination that the third setof amplitude and time criteria are met comprises determining that thesense output signal changes to a voltage between the first voltagethreshold and the second voltage threshold at a fifth time.
 18. Awearable device for detecting gestures, comprising: drive circuitrycoupled to a drive electrode and configured to generate a stimulationsignal, the drive electrode positioned at a first location in the devicefor contacting a first finger of a first hand; sense circuitry coupledto at least one sense electrode and configured to generate a senseoutput signal based on one or more sense signals received at the atleast one sense electrode in response to the stimulation signal, the atleast one sense electrode positioned at a second location in the devicefor contacting the first finger of the first hand; and a processorcommunicatively coupled to the drive and sense circuitry and configuredfor capturing an amplitude of the sense output signal over time, inaccordance with a determination that a first set of amplitude and timecriteria are met, detecting a making of contact of the first finger witha thumb of the first hand, and in accordance with a determination that asecond set of amplitude and time criteria are met following thedetermination that the first set of amplitude and time criteria are met,detecting a making of contact of a second finger adjacent to the firstfinger of the first hand with the first finger or the thumb while thefirst finger and the thumb are making contact.
 19. The device of claim18, the processor further configured for: in accordance with adetermination that a third set of amplitude and time criteria are metfollowing the determination that the second set of amplitude and timecriteria are met, detecting a breaking of contact of the second fingerwith the first finger and the thumb while the first finger and the thumbare making contact.
 20. A method for detecting gestures, the methodperformed at a wearable device including drive circuitry, sensecircuitry, and processing circuitry, the method comprising: generating astimulation signal for propagating through a first finger of a firsthand; generating a sense output signal based on one or more sensesignals received from the first finger of the first hand in response tothe stimulation signal; capturing an amplitude of the sense outputsignal over time; in accordance with a determination that a first set ofamplitude and time criteria are met, detecting a making of contact ofthe first finger with a thumb of the first hand; and in accordance witha determination that a second set of amplitude and time criteria are metfollowing the determination that the first set of amplitude and timecriteria are met, detecting a making of contact of a second fingeradjacent to the first finger of the first hand with the first finger andthe thumb while the first finger and the thumb are making contact.